Valving tube subassembly for percussion bit

ABSTRACT

A rigid cylindrical valving tube having its lower portion surrounded by a resilient member which is secured to the tube to effect a good seal therewith and to prevent gross relative movement in the axial direction. This subassembly is mounted in the upper portion of the flushing fluid passageway of a percussion bit so that the rigid tube projects out of the passageway and above the anvil surface of the bit. The resilient member includes at least a sleeve, which is the part making sealing contact with the rigid tube, and the member also engages part of the passageway wall in both sealing and seating relationship. The seating is accomplished by providing the bit passageway with one or more constrictions or necks of smaller diameter than the subjacent part of the passageway, and by making parts of the resilient members with a diameter larger than that of the contriction-so that after squeezing such part of the resilient member past the neck it will fit under the constriction and be restrained thereby. The assembly furnishes lateral as well as axial freedom of motion to the valving tube, enabling it to make the small but important shifts in position which are necessary to accommodate small and usually transient misalignments between hammer and bit, misalignments which otherwise could result in destruction of the tube by the rapidly moving hammer. The shape of the subassembly also makes field insertion simple and practicable.

United States Patent i191 Nolley 1S4] VALVING TUBE SUBASSEMBLY FORPERCUSSION BIT {75] lnventor: Robert H. Nolley, Houston, Tex.

[73] Assignee: Hughes Tool Company, Houston,

Tex.

[22] Filed: Nov. 23, 1970 [21] Appl. No.: 91,699

[52] U.S. Cl. ..l73/78, 173/80, 277/208 [51] Int. Cl. ..E2lb 1/00 [58]Field of Search ...l73/80, 136, 78; 277/208, 207

[5 6] References Cited UNITED STATES PATENTS Primary ExaminerJames A.Leppink Attorney-Robert A. Felsman [57] ABSTRACT A rigid cylindricalvalving tube having its lower por 1 Feb. 6, 1973 tion surrounded by aresilient member which is secured to the tube to effect a good sealtherewith and to prevent gross relative movement in the axial direction.This subassembly is mounted in the upper portion of the flushing fluidpassageway of a percussion bit so that the rigid tube projects out ofthe passageway and above the anvil surface of the bit. The resilientmember includes at least a sleeve, which is the part making sealingcontact with the rigid tube, and the member also engages part of thepassageway wall in both sealing and seating relationship. The seating isaccomplished by providing the bit passageway with one or moreconstrictions or necks of smaller diameter than the subjacent part ofthe passageway, and by making parts of the resilient members with adiameter larger than that of the contrictionso that after squeezing suchpart of the resilient member past the neck it will fit under theconstriction and he restrained thereby.

The assembly furnishes lateral as well as axial freedom of motion to thevalving tube, enabling it to make the small but important shifts inposition which areneces sary to accommodate small and usually transientmisalignments between hammer and bit, misalignments which otherwisecould result in destruction of the tube by the rapidly moving hammer.The shape of the subassembly also makes field insertion simple andpracticable.

4 Claims, 6 Drawing Figures PATENTEDFEB 6 ma 3.714.993 SHEET 10F aROBERT H. NQLLEY INVENTOR.

BY ATTQRNEY lll. 2w

FIGUREv I PATENTEU FEB 6 I973 SHEET 2 BF 3 FIGURE 2A "In H FIGURE 2ROBERT H. NOLLEY INVENTOR BY awwzfiw1.

ATTORNEY 3,714,993 PATENTEDFEB 6 I975 SHEET 30F 3 as s4 FIGURE 4 ROBERTH. NOLLEY INVENTOR.

ATTORNEY VALVING TUBE SUBASSEMBLY FOR PERCUSSION BIT The presentinvention lies in the field of percussion bits used in penetrating earthformations, drilling through concrete, and the like. More particularly,it concerns a valving tube and its connection to the shank or upperportion of a percussion bit, a connection whereby a portion of thevalving tube is secured in the usual fluid flow passageway extendingdownwardly through the percussion bit and the balance of the tubeprotrudes above the bit for a telescoping connection to the piston of ahammer tool.

In such hammer tool, there is an elongated cylindrical housingcontaining the sliding piston and various other valving structures. Thepercussion bit is mounted with its shank end extending through the lowerend of the housing so that the top of its shank end,.usually called theanvil surface, is disposed below the sliding piston and in a position tobe struck by it as the piston completes its downward or power stroke.The lower or cutting end of the bit extends below the housing in contactwith the rock to be drilled. The axial passageway through the bit servesto direct a flushing fluid to the bottom of the hole being drilled,principally to pick up cuttings and carry them out of the hole by way ofthe annulus surrounding the bit and drill. In addition, such passagewayusually serves as an exit passage for the fluid used to operate thedrill, i.e., to produce the reciprocating action of the piston.

The invention is particularly concerned with that type of drill designedso that, as the piston is descending to strike the anvil surface of thebit, the flow of theoperating fluid into the bit passageway from thespace between the descending lower end of the piston and the anvilsurface of the bit must be blocked. More particularly, the inventionconcerns the type of blockage or valve closing by means of a tubesecured in the bit passageway and extending above its anvil surface sothat, at the proper moment, the upper part of the tube extends into asimilar passageway extending upwardly from the lower or hammer end ofthe piston, making a running telescopic fit which permits flow betweenthe two passageways by way of the tube but effectively traps a portionof the operating fluid between the approaching pair of surfaces (or atleast prevents that portion from passing downwardly through the bitpassageway). Alternately, of course, the valving tube may be secured inthe fluid passageway of the piston with a portion projecting below itslower end to plunge into the bit passageway just before the moment ofimpact.

One problem with such valving tubes is that they are very difficult tomount in such a way that they will not be broken off, either innonoperational handling or in actual service. In operation, the tube issubject to a great deal of vibration, as the hammer blows of the pistonare delivered to the bit at a rate of something like 1000 or more blowsper minute. While the strength of any one blow is well below the yieldpoint of the tube, the repeated blows frequently cause fatigue failureof the tubes.

Another problem in connection with such valving is that of providing asimple means of replacing a worn or broken tube with a new tube in thefield. Combinations heretofore proposed have made use of mountings thatrequire special tools, and the fact that special tools may easily belost, damaged or mislaid points to the desirability of a connectionmeans requiring either no tools or only the most commonly used handtools.

One type of tube heretofore proposed is a stiff tube which is rigidlyconnected to the bit, but such combination has not proven commerciallyfeasible because the tube fails rapidly under service conditions,becoming split or battered so that it must necessarily be discarded andreplaced, a sometimes difficult job depending on the method ofattachment. Another prior art type of tube is one made of a resilientmaterial like nylon. Evidently such tubes are also commerciallyunfeasible, as they, too, are not seen in the market place. Others haveproposed various combinations of rigid materials and resilientmaterials, and the present invention is one of this type.

The broad general object of the present invention is a valving tubeassembly adapted to be disposed in a bit for cooperation with the pistonof a hammer tool (or the reverse) which overcomes the problemsabovementioned.

The present invention provides solutions to such problems in the form ofa rigid, generally cylindrical valving tube having a smaller diameterthan the receiv ing bit passageway and having a resilientsealingcushioning sleeve member firmly secured to its outer surface. Theresilient sleeve may be a simple right cylinder or may be of specialshape, andit must make a reasonably good seal at both its inner andouter surfaces. Further, the sleeve has at least one, but preferably aplurality of axially spaced, radial protrusions that extend beyond thenormal diameter of the bit passageway. This subcombination isfitted intoa bit passageway of generally similar shape, the resilient memberfitting closely or being somewhat compressed between the rigid tube andthe rigid wall of the bit passageway which as groove means to receivethe radial protrusion. Such fit affords a firm seat for the valvingtube, yet at the same time allows it some freedom of movement, bothaxially and laterally. Both degrees of freedom may be necessary when thepiston and bit are slightly misaligned during operation, and theresilient sleeve also serves to reduce the shock loading which otherwisewould be transmitted to the tube as the bit is pounded by the hammertool. The valving tube is easily mounted by placing it above the bitpassageway, placing a protective piece of wood on its upper end, andbeating on the wood with a hammer. In addition, it may be removed. Alubricant applied to the. resilient sleeve and the passageway furtherfacilitates assembly and removal.

To illustrate the invention, several representative embodiments areillustrated in the attached drawing, in

drawing expedient, to obtain clarity in identifying the various parts ofthe bit passageway. i

FIG. 1A is a partial longitudinal section similar to FIGS. 1, 2 and 3but showing an alternate construction of the lower end of the assembly.

FIG. 2 is a similar longitudinal section of a second preferredembodiment.

FIG. 2A is partial longitudinal section similar to FIG. 2 but showing analternate upper end of the assembly.

FIG. 3 depicts a third preferred embodiment, also in longitudinalsection.

FIG. 4 is a longitudinal section of a fourth preferred embodiment inwhich the valving tube and resilient member are se-cured together by amechanical interlock rather than by the use of adhesives, or by bothmeans.

FIG. 1 illustrates one preferred embodiment in which a rigid valvingtube 18, which may be of a metal such as aluminum, is secured in a bit Bso that a portion projects above the anvil surface A of the bit. Apiston P is shown surrounding the protruding portion of tube 18 at theinstant of impact, the piston having just made its power stroke andimpacted on anvil surface A.

As shown, bit passageway 12 and piston passageway 14 are respectivelydefined by walls and 15, which may be of the same diameter, and aredesigned to be disposed so that the center line 16' of bit B is anextension of the center line 16 of piston P. The tube 18 may be a simpleright cylinder resting on the shoulder 29 formed between wall 10 of thebit passageway and the enlarged counterbore 24 at the top of the shankend of such passageway. A number of axially spaced grooves 26 are formedin the counterbore 24, leaving correspondingly spaced lands 28 betweensuch grooves, the bottommost such land being terminated with a roundedportion where it joins the shoulder 29 at the bottom of the counterbore.

The valving tube subassembly includes a resilient sleeve 30 which mayextend axially as shown from the anvil surface A of the bit to thebottom 29 of the counterbore 24, or may be foreshortened at either orboth ends. Sleeve 30 may be of a natural rubber, an artificial rubber,or one of the other relatively soft plastic materials, and is tightlysecured to the outer surface of tube 18 as by adhesives, mechanicalinterlock, or both. The sleeve is preferably but not necessarily ofunitary construction, and includes the upper cylindrical section 32, anumber of axially spaced, radial protrusions or rings or wrinkles 34 oflarger diameter than the upper end portion 32, and a bottom cylindricalsection 38 terminating in an arcuate lower end 39. The rings 34 areformed similar to O-rings and disposed so that they rest very closely inor press against the grooves O-ring type 26 of the counterbore 24, withthe lands 36 immediately beneath each ring facing the correspondinglands 28 of the counterbore. While these lands may also be utilized forresilient seating of the tube in the bit and to further assist insealing, such additional seating and sealing have been found unnecessaryand the facing lands may be separated by the small annular gaps 40.These gaps are beneficial in allowing the resilient rings to more easilydeform during assembly and disassembly ofthe tube in the bit.

For firm but resilient seating against upward movement of tube 18, therings 34 are made with a larger diameter than that of counterbore 24which is the normal diameter of the bit passageway. In the process ofpushing the tube and sleeve into the bit passageway during assemblyrings 34 must be compressed in passing through neck 25 and lands 28 ofthe passageway. After rings 34 are seated in grooves 26, neck 25 andlands 28 effectively restrain the tube-andsleeve subassembly from anygross axial movements, but at the same time the resilience of sleeve 30enables some slight upward movement and some desirable lateral movementor cocking of the subassembly.

The top portion 32 of sleeve 30 may be slightly compressed as mounted toprevent leakage of any operating fluid between the sleeve and the bit,or may be a close fit to minimize leakage.

In the embodiment of FIG. 1, the lower end 23 of tube 18 rests directlyon shoulder 29 of counterbore 24. This metal-to-metal fit limitsdownward movement of tube 18, whereas limited axial upward movement ofthe tube is made possible by virtue of the resilient sleeve 30 beinginterposed between the tube and the passageway wall of the bit. Theresilient member also serves to reduce shock loading on the metal tube18 when the piston P strikes the bit and accelerates it rapidly in thedownward direction.

In the form of the invention illustrated in the partial section of FIG.1A, limited axial movement in both directions is made possible byterminating the lower end of tube 18 above shoulder 29, leaving a smallaxial gap 27. Resilient sleeve 30 may be terminated at the same point,as illustrated in FIG. 1A, or it may be extended to the bottom of thecounterbore and may even jut inwardly to underlie the lower end of tube18'.

In the embodiment of FIG. 2 the same right cylindrical rigid tube 18 maybe employed, but a different resilient sleeve is used, together with adifferent counterbore in the top portion of bit 13,. The counterbore hasnarrowed portion or neck 44, which may extend with uniform diameter tothe top surface A of the bit, but preferably diverges outwardly towardthe anvil surface as shown at 46. Below neck 44 the counterbore isunderreamed to have a larger diameter than at neck 44, taking the formof a right cylindrical surface or groove means 48 for most of the lengthof the counterbore seat. The bottom of this enlarged bore may terminatewith a square shoulder where it joins the wall 10 of bit passageway 12,or may be rounded as at 50 to join the radially extending surface 52which seats the lower end of the rigid tube 18.

Received in such bit socket or seat is a resilient ring 54 which in thiscase takes the form of a right cylindrical shell. Sleeve 54 may be madeof the same resilient material as the sleeve 30 of the FIG. 1embodiment, and is similarly secured to the lower portion of tube 18. Itwill be apparent that in its final seated position sleeve 54 is oflarger diameter than neck 44, and that it must be compressed betweenneck 44 and the outer surface of tube 18 in the mounting process. Thusits upper shoulder is a radial protrusion extending beyond the normaldiameter 48 of the passageway. Although a close fit is acceptable,sleeve 54 in its free condition preferably has a larger diameter thanthat of the underreamed portion 48 of the counterbore, and thus it iscompressed between 48 and the outer surface of tube 18 in its finalseated position to effect a tight seal. As thus compressed, the sleeve54 will be somewhat elongated in the axial direction, with its upper endprojecting into neck 44 to further tighten the seal.

Limited upward movement of the tube 18 is possible because only theresilient sleeve 54 is interposed between the tube and the upper end ofthe passageway. At the lower end of the assembly the metal-to-metal fitof the tube bottom against the shoulder of the counterbore limitsdownward axial movement, but a modification similar to that of FIG. 1Amay be utilized to allow such downward movement.

The partial section of FIG. 2A illustrates an alternate means which maybe used to secure the tube and resilient sleeve subassembly of FIG. 2(and other embodiments) against undesired gross upward movements. Inthis form of the invention, the neck or constriction or groove means ofthe bit passageway is defined by an added member rather than by thewalldefming material of the bit itself, specifically by providing in theconstant diameter bore 48' a groove 58 and a retaining ring 56 insertedin such groove to overlie the resilient sleeve 54. This modifiedembodiment has the advantages of being simple to manufacture and simpleto assemble. Even greater simplicity can be obtained if a retaining ringis used which is press fitted to the passageway wall, making unnecessaryany groove such as 58. As with all other rings, press fitted ring willbe spaced from the rigid tube and overlie the resilient member.

The embodiment shown in FIG. 3 is something of a combination of thesubassemblies illustrated in FIGS. 1 and 2. Thus, the counterbore in theupper end of bit B of FIG. 3 has a narrowed diameter or neck portion 64,above that a portion 66 diverging to anvil surface A and below neck 64 amaximum diameter underreamed portion 68 extending for most of the lengthof the counterbore. As before, the counterbore may terminate with acurved portion 62 joining the radially extending shoulder 63 supportingthe lower end of tube 18. (Also, either the curved portion or the flatportion of the shoulder may be omitted.)

As illustrated in FIG. 3, the resilient sleeve 70 may consist of asmaller diameter upper portion 72 which seats firmly against the neckportion 64 of the counterbore, and a lower portion consisting of acylindrical shell portion having on its periphery a number of verticallyor axially spaced protrusions or rings 74 of larger diameter than theupper portion 72 or normal passageway diameter. Rings 74 in theirnatural state have a larger diameter than that of the underreamedportion 68 of the counterbore, and thus in their seated position shownthey are compressed between tube 18 and wall 68 to provide effectivesealing.

Since in the FIG. 3 embodiment no plurality of grooves are formed in themajor portion 68 of the counterbore which functions as one large groovemeans, most of the restraint against upper movement of the tubesubassembly is obtained through the effective constraint exercised byneck 64,.jutting inwardly as it does to overlie the resilient rings 74of the sleeve member.

As in the previously described embodiments, the rigid tube 18 andresilient sleeve 70 may have lower termini varying from that indicatedin FIG. 3, which shows both of them bottomed out to conform to thecontours 62 and 63 of counterbore 68. Both rigid tube 18 and theresilient-cushioning sleeve 70 may be terminated above shoulder 63 oronly tube 18 can be so terminated, leaving the resilient sleeve 70substantially as shown, bottoming out in the shoulder 62 and roundedcorner 63 defining the lower end of the counterbore.

FIG. 4 illustrates another preferred embodiment, one in which the tubeand its enveloping resilient sleeve are mechanically interlocked by anumber of protrusions on one of these members extending intocorresponding and registering openings in the other member, here shownas rings 84 on outer periphery of rigid tube extending into openings orgrooves 86 formed on the inside diameter surface of resilient sleeve 82.The

means used to restrain the subassembly from gross axial movementrelative to the bit may be any of those previously described, thatillustrated being a series of axially spaced rings 83 on the outersurface of resilient sleeve 82 sealingly engaging the registeringopenings or grooves 87 formed in the bore of counterbore of the bitpassageway. As in the FIG. 1 embodiment, rings 83 are separated by lands81 and grooves 87 are separated by lands 89, and these lands may beeither engaged or face each other across the small gaps 85. While thering and groove engagement between tube and sleeve is shown axiallyoffset from the ring and groove engagement between sleeve andcounterbore, it should be noted that these may be located at axiallyregistering positions.

It will be appreciated that in each of the described embodiments therigid tube 18 (or 80) may be moved somewhat from side to side withoutdamage to itself. Thus, if the piston passageway 14 and the bitpassageway 12 are not perfectly aligned, i.e., centerline 16' of the bitis not a prolongation of centerline 16 of the piston, as the pistondescends it will miss some part of the annular upper surface of tube 18and, at a diametrically opposite point, some portion of tube 18 will bestruck by the beveled entrance to passageway 14 of the piston. Becausethe resilient sleeve can give in one area while it is compressible inanother, the beveled surface will cam the tube 18 into passageway 14 sothat the tube functions as intended. This action will take place withoutbreakage of the tube and may be repeated in many subsequent cycles,similarly without damage. In the absence of such resiliency, i.e., iftube 18 were rigidly secured to the bit, the tube would be broken duringthe first. power stroke of the piston, necessitating a shutdown toreplace the tube.

While no assembly technique is illustrated, it will be apparent that anyone of the illustrated tube subassemblies may be mounted in the bitdesigned for it by simply placing the lower end of the subassembly inthe mouth of the counterbored upper portion of the bit passageway 12, inthe center of the anvil surface. No other tool is necessary than a roughpiece of lumber to protect the upper edge of tube 18 (or 80), and thesubassembly may be driven into position with no other tool than ahammer, axe or its equivalent in mass. The resilient sleeve must becompressed in passing any neck or constrictions defined by the wall ofthe counterbore in the bit (or piston), but once the subassembly reachesthe position where any rings on the outer surface of the sleeve registerwith the corresponding grooves in the counterbore, they will pop intoposition to form the sealing and resilient mounting objectives of theinvention.

Many other embodiments of the present invention will now occur to thoseskilled in the art. The basic components are a rigid, generallycylindrical tube, and a resilient sleeve or sealing-cushioning membersecured to the rigid tube and interposed between it and the walldefining the passageway of the bit. The sleeve and passageway wall mustbe shaped in such a way that a part of the passageway wall or an addedmember secured to the wall overlies at least a portion of the resilientsleeve, so that any operational tendency for the tube-and-sleeve to popout of its seat in the bit will be prevented. It is important that nopart of the side peripheral surface or cylindrical surface of the rigidtube contact the metal wall of the bit passageway, or any metal memberhelping to define the same, for by spacing the tube radially from allother rigid members it is possible to achieve the desired lateralresiliency which gives the tube a long fatigue life.

In connection with those illustrated embodiments of the invention usingone or more resilient rings contacting the wall of the bit passageway toeffect one or both of a sealing relationship and a securingrelationship, it has been found that such rings need not necessarily beintegral with the resilient sleeve, as illustrated. These rings may bemade separately, as indicated by the phantom lines 35 in FIG. 1, withoutdetracting from the sealing and securing efficiency of the assembly,making it possible to use a simple cylindrical sleeve and one or morestandard O-rings.

As used above and in the following claims, a tube or sleeve described asgenerally cylindrical is intended to include all such members havingshapes which may be assembled to the bit (or piston) without specialprocedures. For example, the outside diameter need not necessarily beconstant, but may decrease with a constant taper, as in a generallyconical form, or may decrease in steps. Similarly, the quoted expressionis intended to encompass cross-sectional shapes departing from thecircular, e.g., elliptical, polygonal, etc., so long as the resultingsubassembly appropriates the spirit of the invention.

What is claimed is:

1. In combination with a percussion bit having an anvil upper surfaceand a fluid passageway extending downwardly from said surface, theimprovement which comprises:

a rigid valving tube having one end disposed in the fluid passageway;

a resilient sleeve secured permanently to the exterior of the tube; atleast one resilient, ring shaped protrusion extending outwardly from thesleeve in O-ring fashion to a diameter larger than that of the fluidpassageway;

said passageway including annular groove means to releasably receive theresilient ring and confine the sleeve and tube to the bit.

2. In combination with a percussion bit having an anvil upper surfaceand a fluid passageway extending downwardly from said surface, theimprovement which comprises:

a generally cylindrical and rigid valving tube having one end disposedin the fluid passageway;

a resilient, generally cylindrical sleeve secured permanently totheexterior of the tube, a plurality of resilient, axially spaced, ringshaped protrusions extending outwardly from the sleeve in O-ring fashionto a diameter larger than the normal diameter of the fluid passageway;

said passageway including annular O-ring type groove means releasably toreceive the resilient rings to sealingly confine the sleeve and tube tothe bit.

3. In combination with a percussion bit having an anvil upper surfaceand a fluid passageway extending downwardly from said surface, theimprovement which comprises:

a rigid valving tube having one end disposed in the fluid passageway;

a resilient sleeve secured permanently to the exterior 1 of the tube;

a plurality of axially spaced resilient, ring shaped protrusionsextending outwardly from the sleeve to a diameter larger than the normaldiameter of the fluid passageway;

said passageway including annular groove means to releasably receive theresilient rings; and

said sleeve having an annular gap between each set of adjacent rings andthe wall of the passageway to facilitate ring deformation duringassembly and disassembly of the tube in the bit.

4. The apparatus of claim 21 which further comprises a land means formedin the passageway on the side of each groove means opposite the anvilsurface to provide further sealing against a mating portion of theresilient sleeve.

1. In combination with a percussion bit having an anvil upper surfaceand a fluid passageway extending downwardly from said surface, theimprovement which comprises: a rigid valving tube having one enddisposed in the fluid passageway; a resilient sleeve secured permanentlyto the exterior of the tube; at least one resilient, ring shapedprotrusion extending outwardly from the sleeve in O-ring fashion to adiameter larger than that of the fluid passageway; said passagewayincluding annular groove means to releasably receive the resilient ringand confine the sleeve and tube to the bit.
 1. In combination with apercussion bit having an anvil upper surface and a fluid passagewayextending downwardly from said surface, the improvement which comprises:a rigid valving tube having one end disposed in the fluid passageway; aresilient sleeve secured permanently to the exterior of the tube; atleast one resilient, ring shaped protrusion extending outwardly from thesleeve in O-ring fashion to a diameter larger than that of the fluidpassageway; said passageway including annular groove means to releasablyreceive the resilient ring and confine the sleeve and tube to the bit.2. In combination with a percussion bit having an anvil upper surfaceand a fluid passageway extending downwardly from said surface, theimprovement which comprises: a generally cylindrical and rigid valvingtube having one end disposed in the fluid passageway; a resilient,generally cylindrical sleeve secured permanently to the exterior of thetube; a plurality of resilient, axially spaced, ring shaped protrusionsextending outwardly from the sleeve in O-ring fashion to a diameterlarger than the normal diameter of the fluid passageway; said passagewayincluding annular O-ring type groove means releasably to receive theresilient rings to sealingly confine the sleeve and tube to the bit. 3.In combination with a percussion bit having an anvil upper surface and afluid passageway extending downwardly from said surface, the improvementwhich comprises: a rigid valving tube having one end disposed in thefluid passageway; a resilient sleeve secured permanently to the exteriorof the tube; a plurality of axially spaced resilient, ring shapedprotrusions extending outwardly from the sleeve to a diameter largerthan the normal diameter of the fluid passageway; said passagewayincluding annular groove means to releasably receive the resilientrings; and said sleeve having an annular gap between each set ofadjacent rings and the wall of the passageway to facilitate ringdeformation during assembly and disassembly of the tube in the bit.